摘要:

A feasibility study is performed for a new semiconductor multiple quantum well far‐infrared (THz) laser device, based on selective injection of electrons into an upper subband, and selective removal from a lower subband of a quantum well, using quantum‐well energy filters. Photon confinement is achieved between doped injector and collector semiconductor contacts which also serve as good photon reflectors. The lasing threshold current density is estimated to be in the range ofJth∼130 A/cm2at 5 THz. Thus the feasibility of a far‐infrared laser based on this design and operating at cryogenic temperatures (≤10 K) seems quite promising.

ISSN:0003-6951    

DOI:10.1063/1.105849

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The operation of a diode‐laser pumped thulium, holmium yttrium–lithium–fluoride laser (Tm,Ho:YLF) inQ‐switched mode is reported. Output energies of 220 &mgr;J in pulses of 22 ns duration are recorded atQ‐switch frequencies commensurate with an effective upper laser level lifetime of 6 ms. This lifetime is appreciably longer than that observed in other hosts permitting stored energy extraction of 64%, close to the projected maximum performance from these materials.

ISSN:0003-6951    

DOI:10.1063/1.105850

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Index‐guided self‐aligned InGaAs/GaAs/InGaP quantum well lasers are fabricated by gas‐source molecular beam epitaxy in two growth sequences on a GaAs substrate for the first time. The use of aluminum‐free InGaP as cladding layers permits regrowth steps without the problem with the oxidation of aluminum alloys. A patternedn‐InGaP current confinement layer is used to provide index guiding as well as current blocking. Preliminary results from coated 2.5‐&mgr;m‐wide and 508‐&mgr;m‐long devices show a room temperature continuous wave lasing threshold current of 12 mA with an external differential quantum efficiency of 0.68 mW/mA and a characteristic temperature of 130 K from 30 to 75 °C.

ISSN:0003-6951    

DOI:10.1063/1.105854

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the first observations of large third order optical nonlinearities in AlGaAs/GaAs superlattices due to intersubband transitions. The process is triply resonant when the first intersubband transition matches the radiation from CO2lasers. The intersubband relaxation time has also been estimated from the dispersion of &khgr;(3)with the laser difference frequency &Dgr;&ohgr; and found to be in good agreement with other published values. The magnitude and frequency dependence of the intersubband mechanism have been calculated using the diagrammatic technique.

ISSN:0003-6951    

DOI:10.1063/1.105827

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A nonlinear optical polyester with disperse red side groups exhibited a stable photoinduced birefringence, from 0.14 at 850 nm to 0.21 at 633 nm, after exposure to linearly polarized short‐wavelength visible or ultraviolet light. Thin‐film wave plates, birefringent diffraction gratings and waveguides were written in this polymer using photoexposure. Thin‐ film wave plates of <1 &mgr;m thickness showed ≳&pgr;/4 phase delay and good temporal stability. A 9:1 diffraction efficiency ratio of the two polarization eigenmodes was measured from thin birefringent gratings. This ratio is in good agreement with the theoretical prediction obtained using a simple three‐level model.

ISSN:0003-6951    

DOI:10.1063/1.105828

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The strong confinement of light in planar‐optical waveguides has been used to measure the two‐photon absorption coefficient, &bgr;, in 4‐butoxycarbonylmethylurethane polydiacetylene (4BCMU) thin films. Prisms were used to couple the 30–60 ps pulses (up to 10 &mgr;J) from a mode‐locked YAG laser (&lgr;=1.06 &mgr;m) into the thin‐film waveguides. A simple analytical theory is compared with the experimental results to give a value of &bgr;≊4×10−3cm/MW.

ISSN:0003-6951    

DOI:10.1063/1.105829

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A many‐body theory for the optical susceptibility in highly excited strained‐layer quantum wells is presented. Gain spectra are computed for the example of InxGa1−xAs/InP and different In concentrations, yielding zero, tensile, and compressive strain.

ISSN:0003-6951    

DOI:10.1063/1.105830

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We describe the first results for a hybrid soliton pulse source, combining a mode‐locked semiconductor laser with a silica waveguide external cavity and Bragg reflector. Near transform limited pulses at 1.55 &mgr;m have been obtained at pulse widths and repetition rates compatible with practical soliton transmission system. A novel new mechanism of cavity length detuning is described, which gives the device an extended operating frequency range over which useful mode locking occurs.

ISSN:0003-6951    

DOI:10.1063/1.105806

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The density of ground‐state mercury ions in the cathode region of a fluorescent‐lamp‐like discharge is measured using laser‐induced fluorescence (LIF) at 194.2 nm. LIF is used to make relative density measurements with good spatial resolution and a wide dynamic range while a previously reported absorption technique is used to provide the absolute normalization for these maps.

ISSN:0003-6951    

DOI:10.1063/1.105807

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Direct observations of ions in the laser plume of YBa2Cu3O7−&dgr;impinging onto a substrate surface revealed the increase of heavy species in the plume after multiple laser pulses on the YBa2Cu3O7−&dgr;target. The beginning of heavy species emission from the target was observed at around 100 laser beam pulses (1 J/cm2) in our experiments. Particulate formation at the film surface was observed in the film deposited under this condition.

ISSN:0003-6951    

DOI:10.1063/1.105808

出版商:AIP    

年代:1991

数据来源: AIP